The present invention relates to machine vision vehicle wheel alignment systems adapted with cameras to view optical targets mounted to the wheels of a motor vehicle for purposes of obtaining grayscale or monochromatic images thereof, and for determining vehicle wheel positions and orientations, and more particularly, to an improved machine vision vehicle wheel alignment system utilizing one or more cameras that are sensitive to multiple colors, such as red, blue, and green light to view and obtain images of optical targets associated with a motor vehicle.
Traditional vehicle wheel alignment systems utilizing optical imaging systems, such as cameras, to view and obtain images of optical targets mounted to vehicle wheels, employ grayscale or single-color, monochromatic imaging systems. These traditional vehicle wheel alignment systems utilize cameras or optical imaging systems which are sensitive only to an intensity of received light or to light of a specific wavelength. Such systems, while effective, are incapable of utilizing multiple colors to extract additional information from the images obtained by the camera or optical imaging system.
The majority of traditional cameras and color imagers which are sensitive to colored light use a Bayer pattern mosaic color filter on top of a CMOS sensor or CCD active area. The Bayer color filter is aligned such that a single pixel site on either the CMOS sensor or CCD active area will receive, and accordingly, be sensitive to only one color of light. The Bayer color filter is arranged such that adjacent pixels receive, and are sensitive to, different colors. A typical red, green, blue (RGB) Bayer color filter is shown in FIG. 1. The individual color planes of the Bayer RGB color filter shown in FIG. 1 are set out in FIG. 2 through FIG. 4. Within each color plane of the Bayer color filter, only selected colors of light are permitted to pass through the filter regions, falling on underlying light sensitive pixels elements. The vertical stacking of the multiple color planes shown in FIGS. 2-4 provides for a complete filtering of all light reaching the underlying light sensitive pixels, as is shown in FIG. 1.
To determine multiple color values for each pixel in an image, cameras that employ a color filter such as a Bayer color filter arrangement utilize a complex color interpolation scheme to estimate a red, green, blue (RGB) value for each pixel. The estimated RGB values are based, in-part, upon the filtered colored light received at each adjacent pixel.
Accordingly, it would be highly advantageous to develop a vehicle service system capable of capturing and utilizing multi-color images of color optical targets associated with a vehicle undergoing testing and repair. It would be further advantageous to utilize color target elements to obtain a high degree of precision in the measurement of a detected image, thereby providing a correspondingly high degree of resolution and accuracy in the resulting vehicle measurements.